Control system



. 28, 1943. R. D. JuNKlNs coNTRoL SYSTEM Filed Jan. 5, 1940 6Sheets-Sheet l 304m w w a 4 .L F N r. .m e D n 3 l! lli IIIIII.'

Dec. 28, 1943. R, D, JuNKlNs 2,337,851

CONTROL SYSTEM Filed Jan. 5, 1940 6 Sheets-Sheet 2 llllllllllllllmml um2 I y Slwcmor @IMM Dec. 2s, 1942.` A R. D. JUNKlNs 2,337,851

CONTROL SYSTEM Filed Jan. 5L 1940 e sheets-sheet s VAPOR SEPARATORSUPERHEATER ECONOM|`ZER GENERATING 9 `Il I2 I HEAT SURFACE IO 3| OUTFLOWTs j54 55 xwentor R. D. .Il lNKlNsl coNTRoL SYSTEM Filed Jan. 5, 1940Dec. 28, 1943. 2,337,851

6 Sheets-Sheet 4 CONVERSION SECTION @uw AOW,

Dec. 28, 1943. R. D. JUNKlNs CONTROL SYSTEM y Filed Jan. 5, 1940 6Sheets-Sheet 5 ECONOMIZER GENERATING SECTION coNvEcTloN SUPERHEATERRADIANT SUPKERHEATER Zhwentor Dec. 28, 1943.

R. D. JUNKINS CONTROL SYSTEM e sheets-sheet 6 Filed Jan. 5, 1940ECONOMIZER A GENERATING SECTION ECONOMIZER B SUPERHEATER FIG. 6

nnentor Patented Dec. 28, 1943 CONTROL SYSTEM Raymond D. JunknS,Cleveland Heights, Ohio,

assignor to Bailey Meter Company, a corporation of Delaware ApplicationJanuary 5, 1940, serial No. 312,515'

1o claims.

This invention relates to methods of and apparatus for uid processing ortreating systems, particularly of the forced circulation type whereinthe fluid to be processed or treated is supplied to the inlet of aheated path under pressure and discharges at the other end of the patheither as a liquid, a vapor, or a liquid-vapor mixture. Such systemscontemplate the generation of steam from water, the processing ofpetroleum hydrocarbons, or any analogous fluid treating or processing.

While I have chosen to illustrate and describe as a preferred embodimentof my invention the generation of steam in a forced flow vaporgenerator, it is to be understood that this is by way of example onlyand that the invention is equally applicable to the processing ofpetroleum hydrocarbons or of any fluid in forced flow through a heatedpath.

The particular vapor generators here under consideration are of theforced flow type having a iiuid ow path including one or more long smallbore tubes, in which the flow in the path is initiated by the entranceof liquid under pressure at one end and the exit of vapor only at theother end and characterised by an inflow of liquid normally greater thanthe outflow of vapor, the difference being diverted from the pathintermediate the ends thereof.

Such a vapor generator, having small liquid storage and operated withwide range combustion devices, forms a combination rendering practicalextremely high heat release rates with the consequent ability toeconomically handle practically instantaneous load changes from minimumto maximum, and vice versa, without heavi standby expense, and isparticularly suitable for operating conditions such as locomotive or ma#rine service where load variations are of a wide range and are requiredto be met substantially instantaneously.

The generator has a minimum liquid storage capacity with a maximum heatabsorbing surface so disposed and arranged as to be substantiallyinstantaneously responsive to rapid changes and wide diversities in heatrelease rate in the furnace. The heat absorbing surface, or flow pathfor the working medium, is preferably comprised of a plurality of longsmall-bore tubes with an enlargement, preferably at the end of thegenera-ting section, which acts as a separator to divide liquid andvapor. The vapor is then passed through a superheater, while the excessliquid carried through the tubes of the generatingk section for thepurpose of wetness and preventing scale deposit, is diverted out of theseparator under regulated conditions and is shown as being returned tothe hot Well for recirculation or other usage. It is usual that aportion of the liquid collected in the separator is sent to Waste tokeep the concentration below a predetermined value. The diversion orspillover of liquidfrom the separator is preferably through two paths,one of which is a normal or continuous spillover and the other avariable or adjustable spillover, a1- though the control of suchdiversion does not particularly enter into the present invention.

The excess of liquid over vapor generated, and which may be completelyor partially recirculated, may comprise twenty, thirty, or even fiftypercent of the liquid entering the flow path under pressure. The same istrue in the case of a processing of petroleum hydrocarbons, in which infact the percentage by weight of liquid leaving the heated path may beas much as or greater than the weight rate of Vapor.

In the multi-circuit path of a forced iiow vapor generator'it is usualto introduce now restr1ctors or equalizers between the economizer andvapor generating sections of the path, to attempt to attainequalizationof flow, heating, and other variables through the parallelpaths of the generating section and prevent overheating of one tube ascompared to another. are usually sections oi tubing of relative smalldiameter introducing a resistance to ow of sev eral times that of thetube path following, so that variations in flow resistance of saidfollow-- ing tube path will be of minimized eiiect relative to the totalresistance including the flow restrict-ors. Through multiplying the flowresistance several times in this manner it is, of course, necessary toovercome such resistance with feed pllllp pOWeI. 'l propose to replacesuch iiow restrictors b equalizing valves inserted in the several tubeportions of the paths at the entrance to the vapor generating section,utilizing the pressure drop therethrough to' automatically regulate thesupply oi liquid to the individual paths, and with the knowledge thatsuch a plurality of equalizing valves Will tend to be self-equalizinginsofar as heat and iovvl distributions between the different tube pathsis concerned. Any generating tube which has a tendency, due to unequalapplication of heat for example, to generate more steam than itsparallel tubes tends t0 become overheated through the presence ofgenerated steam within the tubes, rather than a wetting liquid. Whilethe previous flow regtrictors or balancing Flow restrictorsv liquidmixture leaving the tubes.

In particular, the equalizing valve functions to compare the density ofthe liquid leaving the4 economizer section for entrance to the vaporgen- A erating section, with the density of the liquidvapor mixtureleaving the vapor generating section and prior to its entrance to theseparatordrum. From such comparison of densities the rate of admissionof liquid to the particular vapor generating path is controlled, tomaintain the outlet density at or near predetermined value.

No such heat and/or temperature equalizing tendency is obtained withiiow restrictors. When they alone are used, one must depend upon thetotal resistance; that is, resistors plus tube resistance must be nearenough alike in the different circuits to tend to equalize'owtherebetween. Through my invention. by the substitution of equalizingvalves for flow resistors, there is a greater tendency toward circuitequalization of flow, heat. temperature, andV density. since I have notlost the action of pressure drop in equalization of iiows. and at thesame time I have gained an equalization of thermal conditions of thefluid leaving the circuit.

It does not appear necessary to go into the reasons for employing'aplurality of long small-bore tubes for the forced flow path, inasmuch asthis is lwell recognized in the art. Sufce it to say thathavin'g suchconstruction. it is of prime importance that the plurality of circuitsbe equalized insofarV as flow, heat, temperature, density, etc. areconcerned. Y v 'While it is true that I am principally describing mvinvention in connection with a forced circulation vapor generator. itmust be remembered that other treating and processing systems. such forexample as the processing of a petroleum hydrocarbon. also employ aplurality of long smallboretubes for the forced flow path, and hereagain the necessity of equalization of flow. heat, temperature, density,etc. is of prime importance. Again the problem is of great importance inequalization between parallel superheater circuits and paralleleconomizer circuits, etc.

In the drawings: f

e Fig. 1 diagrammatically illustrates a drumless forced ow vaporgenerator to which the present invention isv directed.

' Fig'. 2 is a sectional elevation of an equalizing valve incorporatingmy invention.

Fig, Y3 is similar to Fig. 1, but more completely discloses thedetermination and utilization of density of a mixture of liquid andvapor.

Fig. 4 is a diagrammatic illustration ofthe application of my inventionto a petroleum processing system.

Fig. 5 diagrammatically illustrates the invention applied to a forcedflow vapor generator with a4 plurality of superheater sections.

' Fig.' 6 diagrammatically illustrates the applicationof the inventionto a forced ow vapor generator having aplurality of economizer sections.v The drumless forced now vapor generator to vwhich the presentinvention is particularly directed is diagrammatically illustrated inFig. 1 to indicated gas ilowworking fluid iiow, and heat absorbingsurface, arranged as contained within the enclosure represented by thedot and dash lines.

The ow path for the working medium is comprised of long small-bore tubesbrought together at suitable headers. The generator includes aneconomizer I at the cooler end'of the gas passage and which receivesliquid from a pump which may be connected to a hot well. The pump may beof any suitable type or characteristic adapted for the service.

AThe liquid from the economizer outlet header 2 is conveyed by a tube 3to a manifold 4 from which the liquid is distributed to the generatingsection through, in this instance, three equalizing valves 5 whereby theliquid is proportionately distributed to the tubular fluid flow passages6, 'l and 8 constituting the vapor generating section of the assembly.

These three flow circuits comprising the vapor generating surface joinin a header 9, from which a tube I0 enters a bulge in the uid ilow pathwhich is in the form of a separating chamber II for dividing the iiuidinto liquid and vapor, the

vapor passing to a superheater I2 and the excess liquid beingA divertedfrom the fluid ow path through a pipe I3 to the hot well or to waste.

'I'he heat source is illustratedv as having an oil burner with adequateair admission facilities, but may comprise any well known fuel burningarrangement and have ordinary provisions for initial ignition, safetyfeatures, etc.

'I'he direction of flow of fluid from the header 4 through theequalizing valves 5, the vapor generating passages 6, 'I and 8, theheader 9, and to the separator I I, is indicated in Fig. 1 by arrows andwith single line diagram representing the tubular ow path.

It will be understood that while the vapor generating surface is shownas comprising three parallel flow paths, this is representative only,and the flow paths may be a single path or any desired number of pathsin parallel.

In Fig. 2 I illustrate in sectional elevation a preferred form of theequalizing valve 5, as for example the-valve 5 in connection with thenow path 8 of Fig. 1. In both Figs. 1 and 2 the pipe I4 joins the header4 with the equalizing Valve 5. This flow of water leaves the valve 5through a pipe I5 to the vapor generating path 8, from which it returnsthrough the pipe IG to the valve 5, thereafter leaving through the pipeI1 to the header 9. In Fig. 1 I have indicated a shutoff valve I8 in thepipe I4, and a needle control valve I9 joining the pipes I4 and I5 andby-passingthe valve 5. The purpose of the valves I 8 and I 9 will beexplained more in detail hereinafter.

Referring now specifically to Fig. 2, it will be observed that theheated water from the economizer I enters the valve assembly through thepipe vIl! below a movable valve member 20 having guide ns 2| and seatingnormally on a seat member 22. When the valve member 20 is moved upwardly(on the drawing) water from the pipe I4 passes between the valve member20 and the seat 22 to the pipe I5 in quantity determined by the amountof opening.

Fluid from the heated iiow path 8 may be all water, all steam, or amixture of water and steam, and enters the valve 5 through the pipe I6below a movable valve member 23 having guiding iins 24 and adapted toseat against a seat member 25.

The movable valve members 25, 23 are Interrelated by a p ushgrod k2 6Sldeable through a partition :member 21, The Valve :members 2 0, ..23and .push rod 26 are urged Ytogether'and downwardly by a compressionspring -28 adjustable through the agency of a screw 2 9 in wellhnownmanner. Normally then the valve members 20 andj23 kare urged against theseat members 22 and y25 by the spring 28.

When water under pressure is available inthe 4header 4 the pressureYthus eectivgeupon the underside-of the valve member 20 'Causes it tomove upwardly to unseat and allow iow ,from vthe pipe Ill to rthe pipeI5. VSuch upward positioning moves the push rod 2t, the valve 23, 'andcompresses the spring 28. The result is a flow of liquid through thefluid v.path 8, fthe pipe i6. and the-pipe Il, to ,the header 9,. Whenthe path 18 is heated and-vapor beeinstobe generated therein, the fluidentering-.the valve assembly 5 through fthe pipe I6 constitutes amixture of liquid and vapor at greater specific yvolume and lowerdensity than the liquid passing through the pipes I4 and I5. For acondition of equilibrium this flow of yliquid-vapor mixture requires agreater valveopening vbetween the member y23 and the seat 25, and thusthearea of the-member 23 is greater than that of the member 2l). Thedesign of these relative areas, as well as the initial scale of thespring 2S, and adjustment Aof the screw 29, depends upon the desireddensity -oi the uid leaving the section Sthrough the pipe i6. In otherwords, in ajforcedfflow vapor generator of the type being described, andhaving a separator II, it is desired to admit more water through thepipe I5 than can be evaporated in a single passage through the path S,and the liquidvapor mixture leaving through the pipe I6 will consist ofthe vapor which Ahas been generated plus the excess liquid. This excessliquid may desirably be from 10% to 50% ofthe amount entering the pipeI5, and Ais adjustable within certain limits through the agency of thescrew 29. For wider operating changes it may be desirable to replace thevalve members 20, 23 with valve members of different cross sectionalarea or to change the spring 28.

I have provided an arrangement which is continuous and automatic infunction to control'the admission oi liquid to a ow path, such as `theheated path 8, to continuously maintain a desired density condition ofthe iiuidleaving said ilow path and with adjustment possibilitieswhereby said desirable density may be the denvsity ofthe kenteringliquid, or `the density. of its vapor, Vor ojf a mixture of the 'liquidand vapor. This result is obtained in `generalby utilizing thediierential across a valve of variable opening for 4the control fof ilowvto maintain arpraotioally constant density. I ts utility and ladvantagein connection with a vapor generator of the type herein disclosed willbe apparent, for regardless of the care takenin design of theproportioning and location of the various ow pathsas well as of theheating, there is a possibility that one path may be subjected togreater ormore i direct heating than another path, Vand some means mustdesirably be provided toproportion the liquid among the various paths inaccordance with the heat applied thereto and the heat absorbingcapability of the paths. Furthermore, it is essential that such anarrangement be continuous in operation and entirely automatic in action.The arrangement, vsuchas lI ,have disclosed, satisfies these demands.

I desire it `to be understood-matin speaking O f density 4in thisdescription yand in the claims I use the term in its well understoodandgeneric :dennition'and meaning such as has been established by the:International yCritical Tables, Bureau v'of Standards, and otherauthorities, as fol- "lows:

of temperature, pressure,`loc ation, etc.

Inasmuchas the valve arrangement works primarily ona density or adensity plus kinetic energy basis, the operation will be in thedirection of having a larger percentage of spillover Water fromtheseparator, i. e. unevaporated excesss, at I low pressures than at highpressures.

The unbalanced area and the size of the ports of the two valvesarearranged so that with-the correct steam and water mixture entering -theseparator drum substantially equal water ilows are admitted Ato eachcircuit. In case any one circuit becomes unbalanced and tends to producesuperheated steam, the volume increases'and the pressure drop across theupper valve member increases, opening both -valves and admitting morewater to that particular circuit. Similarly the valves will be closedwhenever there is a smaller percentage of-steam in the mixture enteringthe drum, due to the decrease in volume and pressure drop across theupper valve member In Fig. 1 I show a valve 30 located in a ybypassbetween the pipes I6 and I1. By means of the valves I8, I9 and Slitheequalizing valve 5 maybe-disconnected completely fromthe flow circuit8-soethat work may be done thereon. If the valve I8 is closed, and thevalves I9, 3e are opened, then the equalizing valve 5 is completelybypassed insofar as the flow Apipes Ill, I5, Itand II are concerned. Ifunder ythis condition the needle valve I9 ispositioned by hand to apartly throttled condition, this will introduce an adjustable pressuredrop similar to the known resistors or restrictions and regulation ofthe circuit may be carried on by hand, while the assembly 5 is out .ofservice.

Under certain conditions it may be desirable (with the valve IB openedand the valve 3u closed) to have the valve I9 slightly cracked andvallow ya certain amount of liquid to Icy-Dass the assemblyf. In otherWords, the combination of the assembly 5 in automatic functioning and anadjustable oy-pass I9 allows a wide latitude of regulation of the liquidpassing through the passage 8. IIt will beappreeiated that the vsamearrangement of valves, such as Iii, laand 3il,may be incorporated withthe equalizing valves 5 of the circuits .6 and 'I, orany number ofcircuits -that may be .employed in the vapor generating `both .valvemembers, i. e. with no steam generation, the water flow going completelyt0 the separator or spillover, there will be a vdifferential pressure ofapproximately 36 lb. per square inch across the valve member 2i?, andapproximately 6 lb. per square inch across the valve member v23. At ,themaximum ow rate of approxi-mately SOOOlb. o f water per hour ,past thevalvememn .ber 20,' and of-.say for example 720D 1b. oisteam and soo1b.A of water past the vaivefmemt'er ze,

Ythere will be a differential pressure of approxi-,

Words, this characteristic may be v a lineal orstraight line relation,or may be curved, as deslred.

The upper valve member is designed so that it has an unbalancedv area ofapproximately ten and one-half times that of the lower valve member, sothat even though the pressure drop is less, the actual force exerted bythe upper member is always greater than that exerted by the lowermember. The reason for this arrangement is in order that relativelysmall changes in density of the steam ,and Water mixture, which in turnproduces a change in differential pressure across the upper valvemember, will cause yconsiderable motion of both members, and thusvaffect vthe water flow through the lower member materially.

The lower, or water valve member, is intentionally designed for a fairlyhigh pressure drop, so as to get a similar effect as the balancingresistors or restrictors previously used, though of course a materiallysmaller pressure drop is possible with the present arrangement atmaximum flow. The initial and nal pressure drop can be alteredmaterially by changing the scale or initial tension of the loadingspring. Furthermore', the

characteristic of the valve can be materially altered by changing theports or shape ofthe valve members and seat members.

I have so far explained the functioning of the equalizing valves 5 incontrolling the admission of water from the header 4 to the vaporgenerating surfaces 6, 'l and 8, and in proportioning the water to thevarious surfaces, from manifestations of density at the exit of each ofthe circuits 6, 7 and 8, as well as from a comparison of such densitiesindividually with the density of the feed liquid. A further particularfeature of the present invention is a control ofthe heating responsiveto a determination of the density of the liquid-vapor mixture leavingthe header 9 through the conduit IIJ and passing to the separator I l. Y

In the conduit i0 I have located an orifice or similar restriction 3|,which may be a Venturi tube, now nozzle, or any suitable and well knowndevice for creating a pressure dilerential representative of the volumerate of flow of the fluid therethrough.

Connected to the conduit I at opposite sides of the orice 3| by means ofthe connecting pipes 32, 33, is a differential pressure responsivedevice 34 comprising a mercury U-tube on the surface of one leg of whichis a fioat positioned responsive to, and representative of, thedifferential in pressure existing across the orice 3|. The float isadapted to `position an indicator arm 35 relative to an index 3B, and atthe same time to position a contact arm along a resistance 31.

In similar manner a pressure differential responsive meter 38 isconnected across an orifice 39 in the liquid feed line '3, adapted toposition an zindicator 40 relative to'an index 4|, and to position acontact relative to a resistance 42. As will be explained hereinafter,the resistances 31, 42 comprise legs in a Wheatstone bridge circuit fordetermining the density of the fluid mixture passing the orifice 3|; andsuch determination of density is utilized in automatically controllingthe opening of a fuel regulating valve 43.

I have also indicated in Fig. 1 a thermocouple T1 for determining thetemperature of the fluid passing through the conduit 3, a thermocoupleT2 sensitive to temperature of the mixture entering the separator and athermocouple T3 sensitive to temperature of the steam leaving thesuperheater.

In Fig. 3 I show in more diagrammatic fashion the vapor generator ofFig. 1, and have clearly illustrated how the differential pressuremeters 34, 38 are interconnected to determine the value of density ofthe mixture passing through the conduit l0 to the separator I havepreviously stated that the resistance values 37, 42 are continuouslyrepresentative of differential pressure across the orifices 3|, 39respectively.

The relation between volume flow rate and differential pressure is:

Q=lcM\/2gh (1) Where Q=cubic feet per second c=coeiiicient of dischargeM=lmeter constant (depends on pipe diameter and diameter of orificehole) g=acceleration of gravity=32.17 ft. per sec. per

sec.

h=diiferential head in feet of the owing fluid The coefficient ofdischarge remains substantially constant for any one ratio of orifice diameter to pipe diameter, regardless of the density or specific volume ofthe fluid being measured. With c, M and \/2g all remaining constant,then Q varies as the \/h. rThus it will be seen that the float rise ofthe meters 34, 38 is independent of variation in density or specicvolume of the fluid at the two points of measurement and that thereading on the indexes 36, 4| of differential head is directlyindicative of Volume flow rate. If the conduit size and orice lhole sizeare the same at both meter locations, then the relation of meterreadings is indicative of the relation of density and specific volume.Thus for the same weight rate of flow past the two metering locations,and with a constant water density at orifice 39, the dierential pressureat location 3| will increase with decrease in density of the fluid, andvice versa. v i

This may readily be seen, for if it were desired to measure the flowingfluid in units of weight, Formula 1 becomes:

W=cM \/2ghd (2) Where W=rate of flow in pounds per second d=density inlb. per cu, ft. of the flowing iluid h=di1ferentia1 head in inches of astandard liquid such as water M=meter constant now including acorrection to bring h of Equation 1 into terms of h of Equation 2Assuming the same weight rate of iiow passing successively through twosimilar spaced orifices 39, 3| and with a change in density as may becaused by the heating means, then the density at the second orifice 3|may be determined as follows:

h f) dei des X Thus it will be observed that, knowing the density of thefluid passing the orifice 39 (in this case water, although it may be anyother selected fluid), I may readily determine the density of the uidpassing the orifice 3l from the relation. of diiferential pressuresindicated by the meters 34, 38.

Referring now to Fig. 3 it will be observedA that the adjustableresistances 31, 42 comprise two arms of a Wheatstone bridge. A third armincludes a hand adjustable resistance 44 while a fourth arm includes afixed resistance 45' and an adjustable balancing resistance 4B. Theadjustable resistance 46 (for balancing the bridge) is varied bymovement of an arm 41, through the agency of a reversible synchronousmotor 48, under the control of a galvanometer 49.

The motor i8 is of the self-starting synchronous type of alternatingcurrent rnotor and is shown as having normally deenergized opposed elds.ShouldA the Wheatstone bridge become unbalanced, then the needle of thegalvanometer dii will move either clockwise or counterclockwise (Fig.3), thereby energizing one of the fields of the motor 48, resulting in apositioning of the arm 4l in direction and amount over the resistance t6to balance the bridge and cause the galvanometer needle to return toneutral position. It will be understood that the necessary gearreduction is incorporated between the motor 48 and the arm il so thatthe arm i1 moves at a relatively slow speed.

The Wheatstone bridge thus serves to continuously determine the densityof the fluid at the orifice Si through solving Equation 3. Such densityis continuously indicated on an index G by the movable arm di.

Solving Equation 3 Resistance 37cch31 Resistance 42och3g And it isexpected that:

It is known that the law of the Wheatstone bridge is:

and Rtrepresents dal.

Thus the actual density of the liquid-vapor mixture passing through theconduit I0 to the separator Il is determined and indicatedupon an index5B. At the same time the arm llA positions the stem of a pilot valve 5l,which may be-of the type disclosed `and claimed in the. patent toClarence Johnson 2,054,464, and wherein avfluid loading pressureisestablishedin-the. pipe 52 continuously representative of the value ofdensity of the huid` in conduit l0;

I, have also illustrated that each of the temperature responsivethermocouples T1, Tzand Ta is associatedwith a known potentiometerdevice such as. 53 forl positioning', an indicator 54 relative to aniindex 55 toy advise` the value of the temperature andi at the saineItime position the stem of4 a pilot. valve-such as 56 for establishingafluid loading pressure representative of temperature.

The loadingv pressuresv representative respectively of T1, ."LzJIa` anddensity in conduit luv are manifolded as at` 51' and connect-ed to thefuel supply valve: B3. in' such. a manner that the fuel Supply valve maybef selectively underY the control of any one of the: three mentionedytemperatures or of density of the fluid in conduit lli.

A `particular feature of` my present invention is in the control of theheating: responsive to the value of density ofl the, liquid-vapormixture entering the separator It and for the purpose of maintainingsuch density at a predetermined' value.

Thus considering'thev disclosure of Fig. 3, it will be observed that theplurality of parallel circuits in the vapor generating: portion of the.forced fioW path are each` provided with an equalizing valve 5 servingto regulateY the total feed of liquid tothel generating surface and toproperly proportion itbetween the diierent branches of the parallelcircuits. The heating of the unit however is under controly of the totalliquid-vapor mixture leaving the generating surfaces and passing to theseparator and from an indication of density thereof. Thus while theequalizing valves 5 proportion the totaly feed of liquid to and betweenthe circuits, the hnal value of density of the mixture entering theseparator is used in controlling the heating to maintain said density asdesired.

While in connection with Fig. 3*-1 have explained in detail the mannerin whichl I determine the density ofa liquid-vapor mixture, I do notbelieve thatv itA is necessary to repeat such disclosure, either intheother gures of the drawings or in the description pertainingindividually thereto. It will thus be understood that in Figs. 1, 4, 5and 6 the determination of density of the liquid-vapor mixture may be asexplained in connection. with Fig. 3'.

In Fig. 4 I illustrate in diagrammatic fashion the application of myinvention to the processing of a petroleum hydrocarbon, as for examplein the cracking of oil. Here again in general I illustrate a regulationand proportioning of the feed liquid to the various circuits in theconver-` sion or vaporizing section of the fluid flow path, andfurthermore a regulation of the firing in accordance with. adetermination of the density of the liquid-vapor mixture leaving theconversion section.

The charge liquidv enters through a conduit 3 to a preheating section 58of the flow path, which is heated by a burner or burners 59 having fuelcontrolled thereto byy means of a regulating damper or valve Si). Theheated liquid` passes from the section 58 through a conduit 6I havingpositioned therein an orifice 39 across which is connected adifferential pressure meter 33 for positioning a resistancerepresentative ofi the'v differential pressure;

The heated. petroleum hydrocarbons pass fromk the conduit 6.| to aheader62,- splitting to three `or more parallel circuits comprising aconversion section heated by a burner or burners 63 to which.

vapor separator, or. other relatively quiescent Zone.

68 Where vliquids and vapors. may separate,

The forced flow path is so arran-ged and-proportioned that preferablyno. vaporization. or liberation of gases or vapors. occurs in theheating section 58; and all vaporizati-on or liberation occurs withinthe conversion section `H5. Thus it is normally expected that liquidonly will enter the header. B2 and that a liquid-vapor mixture willleave the header 66 through the conduit 61.

The density of the liquid-vapor mixture in the conduit 6l islcontinuously determined, or a manifestation thereof is. determined,through the agency of the differential pressure meters. 34, 38 and theWheatstone bridge measuring system described in connection with Fig. 3.

Inthe present embodiment I preferably control the fuel valve 60 eithermanually in accordance with an observation of T1 or automaticallytherefrom. I preferably control the fuel supply valve 64 to theconversion section in accordance with density D31 of the liquid-vapormixture leaving the conversion section, or selectively in accordancewith temperature thereof. Y

It should be quite clear that the invention is equally applicable to thevaporization of water, the cracking or other treatment of a petroleumhydrocarbon, or the processing of any fluid.

In Fig. I illustrate a further embodiment of my inventionin connectionwith a forced flow Vapor generator having parallel circuits in thesuperheater, one of which may be a radiant superheatery and the other aconvection type. The feed liquid enters an economizer section afterpassing through an orifice 39 across which is connected the differentialpressure meter 38. From the economizer `section the heated liquid entersa generating section from which the liquid-vapor mixture passes to aseparator II. The density of the mixture entering the separator isdetermined as previously herein disclosed.

Vapor from the separator I I passes to the convection and radiantsuperheaters throu-gh a proportioning valve 69 under the control of atemperature sensitive device 'In for maintaining the nal temperature ofthe steam leaving the unit as desired irrespective of variationsin-load, i

It will be understood that vapor generators equipped with radiantsuperheaters have a superheat-load characteristic differing from thecharacteristic of the convection superheaterrelative to load. Variouscombinations of superheaters having convection heating surface andhaving radiant heating surface have been made in an` attempt to obtain auniform superheat irrespective of load variations. made to proportionthe surfaces vand/or the amount of steam passing therethrough inaccordance with a measure of load to predetermine the proportionality ofsuperheating Work done by the convection and by ther radiant superheaterln an attempt to result in uniform superheat with varying load.

I have found however that a proportioning valve 69 may readily bedesigned and arranged to control from temperature of the total superheatleaving the convection andradiant superheaters to maintain saidsuperheat substantially constant irrespective of load variations.

In Fig. 5 1 control `the nringlin.accordancewithy Some attempts havebeen assassial determination of or manifestation of the'density of themixture of liquid and vapor enterin-g the separator II, and control thetotal feed of liquid to the unit in predetermined excess to measuredvapor outow, the excess liquid being discharged from the separator I I.The flow meter II is a weight rate of flowmeter rather than aV volumeflow meter and has a mercury sealed inverted bell of designed crosssectional area such that the positioning of the indicator and of the airpilot Valve is directly in accordance with weight rate of ow of steamleaving the unit, rather than in accordance with differential pressureacross the orifice 12.

In general then in Fig. 5 the total feed of liquid to the forcedcirculation path is in predetermined excess over measured vapor outflow,which latter of course is determined by the load upon the unit. Thetotal uid passing to the separator I I will be in liquid-vaporproportion determined by the heat applied to the unit and thus I utilizea measurement of density of the liquid-vapor mixture in controlling saidheating to maintain the density as desired. The superheated steamleaving the separator II is then proportioned to the convection andradiant superheaters so that the temperature-of the vapor outflow is asdesired irrespective of load and other fluctuations.

In Fig. 6 I illustrate an embodiment of my invention wherein thecircuits of a forced circulation Vapor generator are arranged with aplurality of economizer sections in parallel. The various parallelcircuits in the economizer section may be located relative to theheating as desired, and the location forms no particular part of thepresent invention. I do however desirably proportion the feed liquid tothe economizer sections in accordance with means similar to thatexplained in connection with Fig. 5. Thus irrespective of the locationof the economizers relative to radiant or convection firing, andirrespective of the proportionality of duty upon the economizers, Iproperly proportion the liquid feed to the economizers through theagency of the proportioning valve 69 by an indication of totaltemperature of the liquid leaving the economizers.

From the economizers the fluid passes through a generating section andto a separator. The density D31 of the liquid-vapor mixture entering theseparator is used to control the firing or heating of the unit, whilethe total feed is in predetermined excess to measured vapor outiiow.

While I have chosen to illustrate anddescribe certain preferredembodiments of my invention it is to be understood that I am not to belimited thereby, but only as to the claims in View of prior art.

What I claim as new, and desire to secure by Letters Patent oi' theUnited States, is:

l. The method of operating a vapor generator of the forced flow typehaving a liquid-vapor separator between the generating and'superheatingportions of the iluid ow path, which includes the steps of heating thepath, normally supplying a selected liquid to the inlet of thegenerating portion in excess over vapor generated therein, dischargingthe'resulting liquid-vapor mixture into the separator, and controllingthe heating in accordance with a determination of density of the uidentering the separator. 1

2. The method of operating avapor generator of the forced ow type havinga liquid-vapor separator between the generating and 4superheatingportions of the. fluid Vliow path,

which includes the steps of heating the path, normally supplying aselected liquid to the inlet of the generating portion in excess overvapor generated therein, discharging the resulting liquid-vapor mixtureinto the separator, regulating the rate of liquid supply in accordancewith a comparison of the density of the liquid supply and the density ofthe fluid entering the separator, and controlling the heating of thepath in accordance with a determination of density of the fluid enteringthe separator.

3. The method of processing a fluid, which includes, flowing the uid ina confined flow path under pressure and subjected to heat, then dividingthe flow into a plurality of parallel paths, heating the plurality ofparallel paths, normally vaporizing a part only7 of the liquid enteringthe parallel paths, utilizing a comparison of the density of the liquidentering the parallel paths and the density of the liquid-vapor mixtureleaving the paths to proportion the liquid to the parallel paths, andutilizing the density of the mixture to regulate the heating of theparallel paths.

4. In a forced flow vapor generator, in combination, a ow path having agenerating portion and a superheating portion, a liquid-vapor separatorbetween said portions, means for heating the path, liquid supply meansnormally supplying liquid to the entrance or" the generating portion inexcess of vapor generated, means continuously determining density of theliquid-vapor mixture entering the separator, and means controlling theheating means responsive to said density determining means.

5. The method of operating a forced flow vapor generator, whichincludes, supplying liquid to the generating portion of the path inexcess over vapor discharged therefrom, passing the liquid-vapor mixtureto a relatively quiescent separator zone, diverting the excess liquid,regulating the heating or the path responsive to density of the mixture,and proportioning the vapor from the separator through parallelsuperheating paths responsive to temperature of the vapor leaving thesuperheater.

6. The method of operating a forced ilow vapor generator, whichincludes, supplying liquid to the unit in excess over vapor dischargedtherefrom, proportioning the liquid through a plurality of parallelpreheating paths responsive to temperature of the liquid leaving suchpaths, passing the liquid through a generating portion of the pathwherein a part only of the liquid is vaporized, discharging theliquid-vapor mixture to a relatively quiescent separator zone, andcontrolling the heating of the zone responsive to density of themixture.

7. The method of processing petroleum hydrocarbon, which includes,serially flowing the fluid through a preheating and a conversion portionof a confined path under pressure and where the conversion portion ofthe path is comprised of a plurality of parallel circuits, continuouslysupplying liquid to the preheateing portion in excess over vapor leavingthe conversion portion, separately heating the portions of the path,regulating the heating of the preheating portion responsive totemperature of the fluid leaving such portion, proportioning the fluidleaving the preheating portion to the several parallel circuits of theconversion portion of the path in accordance with a comparison ofdensity of the iiuid entering each circuit with the density of the fluidleaving each circuit, and regulating the heating of the conversionportion responsive to density of the liquid-vapor mixture leaving theconversion portion.

8. The combination with a petroleum hydrocarbon processing system havinga coniined path including a preheating and a conversion portion seriallyarranged, said conversion portion being comprised of a plurality ofparallel circuits, of means for continuously supplying liquid to thepreheating portion in excess over vapor leaving the conversion portion,means for separately heating the preheating and conversion portions ofthe path, means responsive to the temperature of the fluid leaving thepreheating portion and adapted to regulate the heating of such portionin accordance therewith, means for comparing the density of the fluidentering each circuit of the conversion portion with the density of thefluid leaving each of said circuits and adapted to proportion the fluidleaving the preheating portion to the several parallel circuits inaccordance with such comparison of densities, and means responsive todensity of the liquid-vapor mixture leaving the conversion portion andadapted to regulate the heating of the conversion portion in accordancetherewith.

9. In combination with a forced fiow vapor generator having a generatingportion of the flow path and parallel superheating portions of the owpath serially connected to the generating portion, a vapor-liquidseparator between the generating and superheating portions, meanssupplying liquid to the generating portion in eX- cess over vapordischarged therefrom, means diverting unevaporated liquid from theseparator, heating means for the path, means responsive to the densityof the vapor-liquid mixture leaving the generating portion of the pathand adapted to control the heating means, means sensitive to temperatureof the vapor leaving the superheater, and means proportioning the vaporfrom the separator through the parallel superheating paths responsive tosaid temperature sensitive means.

10. In combination with a forced iiow vapor generator having agenerating portion of the flow path and parallel preheating pathsconnected to the inlet of the generating portion, a relatively quiescentseparator zone to which the generating portion discharges, meanssupplying liquid to the parallel preheating paths in excess over vapordischarged to the separator, heating means for the paths, meanssensitive to the temperature of the liquid leaving the preheating paths,means proportioning the liquid through the parallel preheating pathsresponsive to said temperature sensitive means, and means responsive tothe density of the liquid-vapor mixture entering the separator andadapted to control said heating means.

RAYMOND D. JUNKINS.

